1. Field of Invention
This invention pertains to the art of pneumatic tires and more particularly to reinforcing layers within a tire arranged so as to improve the tire's conicity.
Many pneumatic radial tires are constructed with at least two reinforcing belts and are interposed between the tire's tread and carcass. Typically, the belts are reinforced with cords which cross at angles between 15.degree. and 45.degree. with respect to the circumferential plane of the tire. While this crisscross design of reinforcing cords has many advantages, it can also contribute to a pneumatic tire generating lateral forces. In other words, as the tire is rotated forward in a straight line, certain forces act in a direction perpendicular to the tire's direction, causing the vehicle to vary from its intended course.
One component of lateral force known in the tire industry is "conicity." Conicity can be approximately understood by imagining a cone-shaped tire, tending to roll in a direction other than straight, due to its conical shape.
Tire designers have long sought to reduce or control conicity levels in radial passenger tires. Other designers have created reinforcement belts directed to tire performance parameters other than conicity.
2. Description of the Related Art
In U.S. Pat. No. 5,164,028 to Uemura, a belt is separated by a rubber damper layer disposed therebetween. This design purportedly improves ride comfort and running noise while maintaining the circumferential stiffness of the belt.
In U.S. Pat. No. 3,842,885 to Alban, first and second layers of an elastomeric material are separated by a sheet made of a material with a relatively high modulus of elasticity with respect to the layers. For example, the layers are said to be elastomers while the sheet is said to be a metal, such as stainless steel or aluminum.
Still other belt designs are disclosed in U.S. Pat. Nos. 3,945,421; 4,691,752; 5,014,762 and 5,186,773.
Further improvements over the prior art in terms of controlling or lowering conicity in tires were desirable. Furthermore, manufacturing methods were desired which would allow such improved tires to be manufactured at a high quality and in a cost effective manner.
The present invention provides an improved reinforcement belt structure for use in a pneumatic tire which is particularly well suited for improving conicity in such tires. Also provided is a novel manufacturing method to provide a high quality reinforcement belt structure in a cost effective and simple manner.